Is this on Catalina, if so what version. There are some AppleProResCodecEmbedded calls in the stack trace. Have you upgraded to the latest version of Apple Pro Video Formats? On Mojave and Catalina, this is done in System Preferences>Software Updates.
Some common causes of FCPX crashes:
- Chrome browser. It mis-uses the MacOS VideoToolBox framework. Do not run Chrome while running FCPX.
- Old or buggy plugins. Verify all 3rd-party plugins (esp. CoreMelt) are updated. CoreMelt installers are on this page:
If you are running a beta version of MacOS like Big Sur, that could also cause it.